Metalworking operations include for example, rolling, forging, hot-pressing, blanking, bending, stamping, drawing, cutting, punching, spinning and the like and generally employ a lubricant to facilitate the operation. Lubricants generally improve these operations in that they can provide films of controlled friction or slip between interacting metal surfaces and thereby reduce the overall power required for the operations, and prevent sticking and decrease wear of dies, cutting bits and the like. Sometimes the lubricant is expected to help transfer heat away from a particular metalworking contact point.
Metal working fluids often comprise a carrier fluid and a multitude of specialty additives. The carrier fluid imparts some general lubricity to the metal surface and carries/delivers the specialty additives to the metal surfaces. Additionally, the metal working fluid may provide a residual film on the metal part thereby adding a desired property to the metal being processed. The specialty additives can impart a variety of properties including friction reduction beyond hydrodynamic film lubrication, metal corrosion protection, extreme pressure or antiwear effects, etc.
Carrier fluids include various petroleum distillates including American Petroleum Institute Group I-V basestocks and/or water. Group I basestocks are primarily direct fractional distillation products of petroleum. Group II and III basestocks are further refined petroleum products such as hydrotreated distillation products that have reduced amounts of unsaturation (e.g. less than 1 wt %) and cyclic distillation products. The specialty additives can exist within the carrier fluid in a variety of forms including as dissolved, dispersed in, and partially soluble materials. Some of the metal working fluid may be lost to or deposited on the metal surface during the working process; or may be lost to the environment as spillage, sprays, etc; and may be recyclable if the carrier fluid and additives have not degraded significantly during use. Due to entry of a percentage of the metal working fluid into process goods and industrial process streams, it is desirable if the components to the metal working fluid are eventually biodegradable and pose little risk of bioaccumulation to the environment.
Polymeric polyol esters exhibit compatibility with and some solubility with both hydrocarbon oils and water carrier fluids, depending on molecular structure, molecular weight etc. The polymeric polyol esters are biodegradable and if they do not contain other heteroatoms pose little risk of bioaccumulation. Polymeric polyol esters from pentaerythritol are known as additives for metalworking but suffer from compatibility problems at some temperatures with some lubricant basestocks materials.